The use of delivery devices employing catheters has long been known for a variety of medical procedures, including procedures for establishing, re-establishing or maintaining passages, cavities or lumens in vessels, organs or ducts in human and veterinary patients, occlusion of such vessels, delivering medical treatments, and other interventions. For these procedures, it has also long been known to deliver an implant by means of a catheter, often intraluminally. For example, a stent, stent-graft, filter or occlusion device may be delivered intraluminally from the femoral artery for deployment.
For procedures in which a prosthesis or other device is implanted into a patient, the device to be implanted is normally held onto the catheter in a compressed state and then released from the catheter so as to expand to its normal operating state, prior to withdrawal of the catheter from the patient to leave the implant in position.
A variety of delivery mechanisms is known in the art. These generally involve positioning the implant on a distal part of a delivery device, that is, at an end furthest from the external manipulation end used by the clinician during the deployment procedure. The prosthesis or implant is normally held at the distal end of the catheter by a suitable restraining mechanism, restraining wires being just one known example. It is also conventional to cover the implant with a sheath in order to protect the implant and also the patient's vasculature or organs during the delivery process. Once the implant has been positioned at the location in which it is to be released, the sheath is retracted along the catheter to expose the implant. The implant is then expanded, either automatically, if the implant is of the self-expanding type, or by a suitable expanding mechanism if not, such as by means of an expansion balloon.
In cases where a sheath or other covering is provided, some delivery devices include a mechanism by which the sheath can be withdrawn by being pulled back towards the external manipulation end of the delivery device, that is, towards the surgeon or other clinician. The force required to withdraw such a sheath may be very large. Furthermore, the resistance to withdrawal of a sheath may vary, which can cause problems for a controlled and safe release of an implant.
The sheath may be withdrawn by the surgeon or clinician gripping the proximal end of the sheath with one hand, and the catheter with the other hand, and pulling back the sheath relative to the catheter. This method is not only hard work, but also the surgeon or clinician is unable to exert much control over the withdrawal process. Moreover, use of such force to withdraw a sheath may result in shifting of the previously carefully placed implant.
Known implant delivery handles are disclosed in U.S. Pat. No. 5,707,376, US 2007/0060999, US 2005/0060016 and U.S. Pat. No. 7,052,511.